\section{Conclusion}\label{sec:conclusion}
In this paper,  we expect to provide a trust metric which can capture trusts and form a computational model from both individual aspect and collective aspect. We showed that by dividing trust into 2 levels and 3 types: each one of them is updated and propagated with different policy, a more accurate and agile trust estimating framework is achieved. We derived a lots of our work from studies in psychology, especially Deutsch's hypotheses. Though testing our model against a dataset from an OSN, we demonstrate that our trust metric, combined with subjective and objective views, satisfied demands of OSN, such as decentralized structure and highly dynamic interactions. Finally, we extent our model in a broader scale, which reflects a wider map of rational trust in psychology. With acknowledge and address important hurdles so far, we expect future researches can reach full capacity of our model. 

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